Low density cellular explosive foam and products made therefrom



July 29, 1958 ,v STARK 2,845,025

LOW DENSITY CELLULAR EXPLOSIVE FOAM AND PRODUCTS MADE THEREFROM Original Filed Sept. 20, 1950 3 Sheets-Sheet 1 v n k Ndt INVENT OR mmuooE 8.5 6: Al

32 26mm wzmaixm 3 $2.52

mm QN\\ mmuQOE 025 62 25mm mzwodxu l H uZwqEXm HOWARD J. STARK mi 22 r wzmsmxm 6 29.238

ATTORNEYS July 29, 1958 2,845,025

' H. J. STARK LOW DENSITY CELLULAR EXPLOSIVE FOAM AND PRODUCTS MADE THEREFROM Original Filed Sept. 20, 1950 3 Sheets-Sheet 2 DETONATOR HIGH 4 EXPLOSIVE FIG. till DETONATOR VIARHEAD Foam- :0 EXPLOSIVE 74 72 unema :5:

HIGH EXPLOSIVE FIG. Z

INVENTOR HOWARD STARK ATTORNEYS July 29, 1958 H. J. STARK 2,845,025

LOW mausm CELLULAR EXPLOSIVE FOAM AND PRODUCTS MADE THEREFROM Original Filed Sept. 20, 1950 3 Sheets-Sheet 3 FOAMED EV I r:

EXPLOSIVE Q m INVENT OR HOWA RD .1. STARK cellular buoyant explosive.

- "increased hig Howard LStark, Arlington, Va.

United Srat s miOfi5 i I j CQntinuation of abandoned application Serial No.-

185,900, September '20, 1950. This 23, 1954, Serial No.-45 1,723 i 2 Claims. (11, 102 (Granted under Title 35,, U. 5. Code 1 m. 266) pplication August The invention described herein may be manufactured and used by or for the Government of the United States Thisinvention relates to. lowde us y e p fl ives audit I particular to the use of ow' den ty, cellularfi xplos y a of America forrgovernmental pu pQses;wiIhQutthcpaymea f's uy oy l ies; thereqn :orhe ior.

, v This, is a continuation pp icaticn based, Qn mycp adinsv ppli ation; Ser al. N 18 9100afi ed S p mbe :29,

11950 now abandon nd ent tled Lew De i r Qell lar V Y a n The general object of the inventlon is to provide an explosive having acellula fic m s ructu e whi h b cause cf suchfioam s ure,- isv relat y a d nsiw is hues nt th p cto atec, an. .ofg; a erand l QI rapid s atter n e f t-than the, sa e we ht o high expla ivehav ng a ellula pam tructure hi h may be shape. ptigr t the setting cas -or mol e n a particular wor;assumption of rigidity. t v p r 7 It. is a di i nal object. of he inven ion t t-p ovide .ior products wh ch re? made impart-oi a q m d .or

,--jQther jectives. will b app ren from, th tqllqw n descrip i n nd from thedraw i g heretq attached; which are illustrative of, the method cfimalsing he ellula exticn. v

n hese irawingsz r .r ri 1 .is a flow, char ct'thedynanic ai rs' meth plosive and of.thepreferredv embodiment f the invenof hi invention;

e 2 is a f ow h r of the chemicalblqwiugj method is, invention;

"transverse sectio th eu ii a v .r p e ll t at df y F g-" butc ng a relatively large quantity; of the toarned explo;

' siv at h s invent t n. s t

"'Fig. '5 is a diagrammatic 'sectional-elevatiohal view' i'of a fioating mine in which the shell is comprised. ofg the "folded foamed explosive of thisjinvention; encased in 'of construction;

nation to .provide. an

3 is a diagramma c an er e scct bn hmughf tiweig htjmetal' or impregnated fabri'c arrdishows the r w h explosive charge, possible with :thisj type I explosive charge, of the conventional high'density explosive withthe foarned explosive of this invention; I v

v jFig. 7. is a diagrammatic longitudinally sectional eleva I i't'i'onal view ofa torpedo carrying a charge'of high density "explosive and'fqamed explosive of this invention; and

Eig's. 8,and 9 are avdiagrammatic longitudinalseetionalje levational view andatransverse "sectional view taken on "to as closed-cells'in contradistinction tospongy openejcells. 1

atiYilY I 'meric methyl methacrylate is idealiy line 9-9 of Fig. 8 respectively er a raidi homing? vessel showing the "foamed" pl invent-ion cast "and molded within the stru 'la r acetate. It is relatively stroriggandtriug'h a e 0 density thereof can be varied formulation range of from about 5 to aboutfSOpbundsperj v The cells of the 'foamed; and set struc tilrelo plosive are substantially'non conrmunicating{and Therefore, a-molded plate of this material is impervious to gas andwater. In compariso H I wood, which has ajbuoyancyof abouttwenty po cubic foot aftentwentyfourhours immersion u e 'foot head of water, thiscellular explosive 'lras a b of from about 20 to about 50 pounds ;per cubic too similar conditions. The following explosives can be prepared cellular form: V i

('1) Trinitroto'luene ('2) Nitrocellulose (tri, hexaand dodek (3) Pentaerythritdl y (4) RDX (cyclotrimethylei etrinitramine) The foamed explosive consists essentially dfE-any of; the above explosives bonded by a thermoset'tin' This inventor has foundjthat polyestersof e'th maleic anhydride inter-mixed withmo'no' the carrying out of this invention fThi and described along with: other resins h suitable in Carleton Ellis'fiPatent 2-,255'

corporated by reference-and formsa part ofthis s pecifiea 0 tion. Of course a filleras used in'the jexamples is unnecessary and not: used althou'ghsuc still fall within the scopeof what is considered 7 present invention. These-"bonding th r mo'setting p0 ester resins are well known in the fi eld oi resin and their specific compositions form rio- 0 vention. The requirements thereof patible with solutions of the eiiplosivesfthat room temperature in a relatively s hort perio such as about fifteenminutes,set perman tly one hour and thatthey impart a viscosity t of the explosive suflicient to prevent the 'escap therefrom and yet be sufi'icient-ly'fiuidfo'r'r efiici ing and casting. The rater-0f setting gof t-hes'e with the solution ofth'e resinandthe xplos ve"and I i rate "of curing desired. Also-an accelerator;

balt riaphthanate-finay be added in a propr-tional zinib ifi F us: controlled by the addition thereto of afr'elat iyely marl-1 allowed to rest for about minutes.

of from about 2% to about 5% by weight to give additional control on the rate of gelling and setting of the resln.

Commercially available resins which have been found to be suitable as a bond for the foamed explosives of this invention are MR-28C and 29C by Marco Chemicals, Inc., Selectron 5003 and 5016 produced and marketed by the Pittsburgh Plate Glass Company, Laminac 4128, 4129 and 4116 produced and marketed by the American Cyanamid Company, and Paraplex P-43 by Rohm and Haas Company.

Two methods of the preparation of foamed explosive are preferred by this inventor. These are-(1) the socalleddynamic air-set method, and (2) the chemical blowing method. These methods differ from each other mainly in the method of introduction of air or gas into theresinous solution of the explosive. In the dynamic air-set method (reference being had to Fig. 1 of the drawings), asolution of the explosive in styrene, ether, acetone, or a mixture of some of these solvents is made as indicated at 10. Only as much explosive may be dissolved as will go into the solution with or without the application of a moderate heat, and with staying below the decomposition temperature of the explosive. A solution of a polyester type resin, curing agent or catalyst and accelerator is prepared as shown at 12 in the proportionate amounts above indicated. From about to about 30% by volume of the liquid resin solution is mixed with the solution of the explosive as shown at 14. The curing agent and accelerator will cause the resin to gel in about 15 minutes and to set permanently in about one hour. The mixture of solutions of the explosive and resin is stirred for about 5 minutes as indicated at 15 and Compressed air from a source (not shown) is introduced into blowing chamber 18 and thence through foraminous member 20 which may be a glass frit or metal screen of a mesh in the range of from 75 to 300 and through the mixture at 14 for about 3 minutes which will foam the said mixture. The foamed mixture is then poured into molds or other containers within the remaining 2 minutes of the 15 at which time the foamed explosive gels or sets up and in one hour becomes a hard cellular mass. By a proper control of the viscosity of the mixture, above referred to, air bubbles do not appreciably escape therefrom after the completion of the blow or during the period that the mixture is in the mold prior to gellation. There is therefore no collapsing of the foamed structure in the mold.

In the chemical blowing process the explosive is dispersed in a suitable solvent such as acetone or styrene as indicated at 24 in Fig. 2 to obtain a saturated or highly viscous solution. The solution of the resin is prepared by the addition of a curing agent and an accelerator in the proportionate amounts above indicated and as shown at 26. The resin may be a polyester type resin as above described or it may be of the alkyd peroxide curing type. In either case they are adjusted to gel in about fifteen minutes and to set in about one hour as in the process above described. The solutions of the explosive and the resin are conducted into mixing chamber 28, the solution of the resin being added in the proportion by volume of from 10% to 30%. In this chamber there is added to the mixture from 10% to 30% by volume of a chemical blowing agent such as diazoaminobenzene or toluene diisocyanate. The mixture is stirred, as indicated at 30 for from five to ten minutes and is then poured or cast into molds as indicated at 32. The molds are then heated as indicated at 33 to a temperature of about 120 C. but not above decomposition temperature of the explosive at which temperature the blowing agent evolves a relatively large volume of gas which causes the mass to expand forming a cellular structure.

The range in composition, on a percentage weight basis at various temperatures of formation, of the foamed immediately prior to the gelling thereof.

4 explosives of this invention is given in the following table:

Percent Percent Percent O. Solvent Range Explosive Range in Range in Temp. in Comp. Comp.

Comp. of Resin acetone 10-10 T. N. 'I -60 10-30 70 PETV 25 5 50 PETN 40 10 t0luene 6O PETN 30 10 25 eyclohexanone 78 RDX 12 10 60. acetone 67 RDX 18 15 97- 60 RDX 25 15 25- 78 HBX- 12 10 60 67 HBX-l dz 2". 18 15 97 cyclohexanone 60 HBX-l dz 2 25 15 Referring further to the drawings, In Fig. 3 a conventional floating mine is shown diagrammatically and generally at 40. The mine comprises a metallic case 42, contact elements 44 which are in electric circuits 46 with the detonating or exploding device 48. This exploding device detonates the charge of high explosive 50 when any one of the elements 44 is actuated by contact with an object in the water. The interior volume of this type of mine is comprised of about 50% air space as shown at 52.

In Fig. 4 the air space of the mine shown in Fig. 3 is filled with the foamed explosive of this invention as shown at 54 which has been cured and set in place. This foamed or cellular explosive not only gives an additive effect to the brisance of the high explosive, but in the event of leakage through metallic shell 42 due to erosion or corrosion thereof, the buoyancy of the mine will be maintained substantially as that existing when the mine is in leakproof condition.

.Fig. 5 is illustrative of an embodiment of this invention in which the shell of the mine is comprised of molded cellular explosive 56 covered on the exterior and interior faces with relatively thin layer of metal or impregnated fabric 58. The increased buoyancy of this type of construction over the conventional, heavy metallic case mine is readily apparent. In fact, the buoyancy isso much greater that substantially the entire interior space of the mine may be filled with high density explosive thereby producing a mine of greatly increased shattering effect when also considered in the light of the additive explosive effect of the cellular explosive comprising the shell.

Fig. 6 is a sectional illustration of a floating harbor mine showing the arrangement of a metallic casing 60, a high density explosive charge 62, detonating or exploder device 64, actuating contact element 66 and foamed explosive of this invention 68 surrounding the high explosive charge and exploder device and filling the air space normally present within the casing of this type of mine. In the event of leakage of water through the casing due to corrosion thereof or otherwise, the foamed explosive prevents loss of buoyancy and the normally resultant loss of the mine.

Fig. 7 is a sectional-elevational view of a torpedo shown generally at 70 in which the foamed explosive 72 of this invention fills the normally present air-space within the shell 74. The legends in this figure are believed to be self-explanatory. In this embodiment of the invention, the overall buoyancy of the torpedo is less than that of ,the torpedo having the conventional air space. But the total shattering effect of the explosion is much increased by this additional quantity of foamed high explosive. In charging this cellular explosive into this air space in the torpedo, the foamed explosive is poured into this space The space -is completely filled and upon the curing and setting of the 5 resin component the cellular explosive becomes rigid and reinforces the sidewalls of the shell.

Figs. 8 and 9 show the application of the foamed high explosive of this invention to the structure of an electronically controlled homing vessel in sectional-elevational views. Here the double walled hull 90 is shown provided with radio control 92 for motor drive mechanism 94. High density high explosive 96 substantially fills the interior of hull 90 surrounding the exploder device 98. The detonating contact element is shown at 99. The

space within the double wall structure of the hull is filledwith the foamed high explosive of this invention as shown at 100. As in the case of the torpedo above-described, the foamed explosive is poured into this hull wall space immediately prior to the gelling and after setting the foamed cellular explosive mechanically reinforces the structure. The advantage of this type of construction of these homing vessels is that the shattering effect of the explosion is greatly increased and that in the event of leakage through the outer wall of the hull due to corrosion or to any other cause the buoyancy of the vessel is maintained.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that it is intended to cover all changes and modifications of the examples herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention as set forth in the appended claims.

I claim:

1. A floating mine comprising a casing, a detona'tor mechanism carried with said casing, a solid high explosive carried inside part of said casing and'a foamed water impervious buoyant explosive, the cells of which are substantially non-communicating, filling the remaining space in said casing.

2. A floating mine comprising a casing, a solid high explosive occupying a portion of said casing, detonating means therefor occupying a further portion of said casing, and a foamed water impervious buoyant explosive, the cells of which are substantially non-communicating, filling the remainder of said casing, said foamed explosive adding to the shattering effect of said high explosive and serving as a buoyant means for said mine.

References Cited in the file of this patent UNITED STATES PATENTS 1,278,420 Barbosa Sept. 10, 1918 2,062,011 Norman et al Nov. 24, 1936 2,271,185 Dunajefi Jan. 27, 1942 2,537,039 Downard Jan. 9, 1951 2,541,389 Taylor Feb. 13, 1951 FOREIGN PATENTS 916,465 France Oct. 19, 1946 

1. A FLOATING MINE COMPRISING A CASING, A DETONATOR MECHANISM CARRIED WITH SAID CASING, A SOLID HIGH EXPLOSIVE CARRIED INSIDE PART OF SAID CASING AND A FOAMED WATER IMPERVIOUS BUOYANT EXPLOSIVE, THE CELLS OF WHICH ARE SUBSTANTIAL NON-COMMUNICATING, FILLING THE REMAINING SPACE IN SAID CASING. 